The invention relates to a polarized electromagnetic relay with magnetic latching, notably of a trip device for an electric circuit breaker, comprising:
a fixed magnetic circuit made of ferromagnetic material comprising a tubular frame affixed at its opposite ends to a first and a second parallel flange, extending perpendicularly to the longitudinal axis of the frame,
an annular permanent magnet with axial magnetization whose coplanar front surfaces of opposed polarities come into contact respectively with the internal wall of the first flange and one of the faces of a magnetic flux-diverter,
a moving armature mounted to slide axially according to the direction of the longitudinal axis between a latched position and a released position, said armature being urged into the released position by a return spring and in the latched position being pressed against the flux-diverter by the magnetic attraction force of the permanent magnet which is of greater intensity than the bias of the return spring,
an actuating member associated with the armature and passing axially through an opening in the second flange, the armature and actuating member assembly forming the moving assembly of the relay,
a first axial air gap corresponding to the gap between the flux-diverter and the moving armature,
a trip coil mounted coaxially on an insulating bushing inside the frame surrounding the moving armature and extending axially between the flux-diverter and the second flange, excitation of said coil causing in the magnetic circuit a magnetic flux which opposes the polarization flux of the permanent magnet in the first air gap, so as to release the armature and enable it to move from the latched position to the released position by means of the return spring.
According to a prior art device of the kind mentioned, the return spring of the moving armature is fitted outside the magnetic circuit, and the axial length of the coil is smaller than that of the permanent magnet. The high reluctance of the magnetic circuit in the latching position of the armature requires a high tripping flux which increases the coil tripping energy. The use of a relay of this kind in an own current trip release is dependent on a large trip signal obtained either by amplification or by larger current sensors.
The object of the invention is to overcome these disadvantages and to provide a trip relay having high sensitivity and reduced dimensions.